It has been established that the most likely period of breakthrough wave occurrence is the time of spring flooding or heavy rain when water-head facilities are subjected to significant loads that lead to the collapse of their individual elements or the entire structure. In addition, the possibility of man-made accidents that can occur at any time cannot be ruled out.
It has been proven that breakthrough wave formation depends on the nature of the destruction or the overflow through a water-head facility. For the study reported in this paper, a model of the kinematics of riverbed and breakthrough flows was used, which is based on the equations of flow, washout, and transport of sediments that are averaged for the depths of the stream. The differential equations describing the nonstationary flow averaged for depth are solved using the numerical grid system FST2DH (2D Depth-averaged Flow and Sediment Transport Model), which implements a finite-element method on the plan of a riverbed's topographic region. These tools are publicly available, which allows their wide application to specific loads and boundary conditions of mathematical models.
The construction of an estimation grid involving the setting of boundary conditions and the use of geoinformation system tools makes it possible to simulate the destruction of a culvert of the pressure circuit and obtain results for a specific case of an actual riverbed and a water-head facility.
It has been established that there is a decrease in the speed of wave propagation along the profile, from 3 m/s to 1 m/s.
The impact of bottom irregularities, the effect of floodplains, and the variety of bottom roughness have also been assessed, compared to the results of their calculation based on one-dimensional models given in the regulatory documents.
Hydraulic calculations were carried out taking into consideration the related properties of the main layer of the floodplain, which consists of peat accumulations, and the heterogeneity of the depths and roughness of floodplain surfaces of soils. It has been established that there is almost no erosion of supports in the floodplain zone in this case.
It was found that as the distance between the flow and breakthrough intersection increases, there is a decrease in the height of the head from 2.1 m to 1.25 m.
Introduction. The article presents the results of the study of irregular bottom river forms and foundations of structures, as well as coastal forms under the action of surface channel currents. It is assumed that the development of channels occurs due to the action of natural hydromorphodynamic river processes during the long stages of rivers existence formed in accordance with topographic, geological and hydrometeorological conditions. Problem Statement. Flow velocities are determined by a system of equations for the kinematics of channel flows and sediment transport, which is built on the basis of averaging the depth of flow. Purpose. Application of the developed methods of solving problems in the spatial dimension for the study of turbulent effects in the interaction with structural elements. The development of methods for applying the spatial model will be carried out at the next stage. Methods of research. Differential equations describing a nonstationary depth-averaged flow are solved using the FST2DH numerical model, which implements the finite element method. The steps typically performed when using FST2DH to study surface water flow and sediment transportation require the general necessary geographic information systems to build a network and assign boundary conditions. The equations for calculating channel erosion and erosion of bridge piers in bound soils are also considered, where it is shown that erosion depends more on soil properties than for the case of incoherent sediments, but can reach the same erosion depths with longer multi-flood calculations hydrographs. Results. Calculations of the flow kinematics of the calculated floodplain on the example of crossing the floodplain along the highway showed that the presence of a large angle of the overpass to the flood flow leads to additional conditions for increasing local erosion of supports in the form of solid rectangular columns. Significant local erosion is observed in the area of supports near the channel part. Conclusion. Based on the calculations and analysis of the kinematics and hydromorphodynamics of flows in the area of the designed bridge, recommendations on the necessary layout and design protective measures have been developed. Keywords: channel processes, erosion of bound and unbound bottom soils, erosion of piers bases of bridge crossings and overpasses, numerical methods.
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